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2017 Conference

Abstract Number: 51 | ID: 2017-51

In Utero Dioxin Exposure and Thyroid Hormone Levels in the Seveso Second Generation

Marcella Warner( Center for Environmental Research and Children's Health, School of Public Health, University of California, United States, mwarner@berkeley.edu), Stephen Rauch(Center for Environmental Research and Children's Health, School of Public Health, University of California, United States), Paolo Mocarelli(Department of Laboratory Medicine, University of Milano-Bicocca, School of Medicine, Hospital of Desio, Italy), Paolo Brambilla(Department of Laboratory Medicine, University of Milano-Bicocca, School of Medicine, Hospital of Desio, Italy), Stefano Signorini(Department of Laboratory Medicine, University of Milano-Bicocca, School of Medicine, Hospital of Desio, Italy), Brendda Eskenazi(Center for Environmental Research and Children's Health, School of Public Health, University of California, United States)
Background/Aim: In animal studies, prenatal TCDD exposure alters thyroid homoeostasis and thyroid hormone concentrations; epidemiologic evidence is limited. The Seveso Women’s Health Study (SWHS) of women exposed to a single high dose of TCDD during or before their child-bearing years is unique. Initial, individual-level TCDD exposure measures are available for this first-generation cohort. Nearly 40 years after the explosion, data collection to follow up the second generation of the SWHS cohort is complete. We aim to examine the relationship of in utero TCDD exposure with thyroid function among SWHS children.
Methods: We included 429 children who were 18+ years with complete follow-up data, including a fasting blood draw. Serum levels of total thyroxine (TT4), free thyroxine (FT4), free triiodothyronine (FT3), and thyroid stimulating hormone (TSH) were measured using immunoassays. In utero TCDD exposure was defined in two ways: 1) TCDD concentration measured in maternal serum collected soon after the explosion and 2) TCDD estimated at pregnancy.
Results: The children (223 female, 206 male) averaged 28.6 (±6.0) years of age. A 10-fold increase in TCDD estimated at pregnancy was negatively associated with FT3 (adj-β=-0.11, 95% CI -0.19, -0.02), but not FT4 (adj-β=-0.26, 95% CI -0.60, 0.09), TT4 (adj-β=-0.19, 95% CI -0.58, 0.20) or TSH (adj-β=5.4%, 95% CI -8.7, 21.6). Stratifying by child sex, TCDD estimated at pregnancy was positively associated with TSH among daughters (adj-β=21.7%, 95% CI -0.9, 49.5), but not sons (adj-β=-11.0%, 95% CI -25.1, 5.8) (p-int=0.02). Results were similar when we considered initial maternal serum TCDD concentration, but less significant. Results including the SWHS children under 18 years, will be presented.
Conclusions: These results suggest in utero exposure to TCDD, a potent endocrine-disrupting compound, may alter thyroid function later in life, in this case decreased FT3 levels and increased TSH levels in daughters exposed to TCDD.